Activation of n → π* Transitions in Two-Dimensional Conjugated Polymers for Visible Light Photocatalysis

In semiconductor-mediated photocatalysis, the optical property of semiconductors is a key parameter and closely related to the conversion efficiency of solar energy. However, endeavors in achieving a wide spectral response of semiconductors are still limited in impurity incorporation or using other assistants. Here, we report on a structure-distortion-induced extension in the optical absorption of conjugated polymer semiconductors without relying on any extra species, by taking a typical example of two-dimensional graphitic carbon nitride (g-C3N4) nanosheets. Experimental and theoretical calculation results both identified the close relationship between the band structure and the structural distortion and the amount of the layers, while keeping in-plane fundamental units intact and the connecting mode invariable during the peeling process. Photocatalytic activity was evaluated toward hydrogen evolution over different samples with visible light. The results showed that distorted g-C3N4 exhibited higher activity and its wavelength-dependence activity can be extended to 550 nm with desirable H2 production. This finding offers a new channel for researchers to design a polymer with photocatalytic activity under its extending visible spectrum.